1. Field of the Invention
This invention relates to a signal processor including a circuit receiving a detection signal through a coaxial cable from a sensor unit having a detecting element and performing processing of the detection signal such as by amplifying the same. More particularly, the invention relates to connection of the coaxial cable to such a signal processor.
2. Description of the Prior Art
Sensors such as photoelectric switches or proximity switches are divided into two types, that is, an amplifier built-in type in which a sensor unit provided with a detecting element incorporates an amplifier unit for processing an output signal from the detecting element of the sensor unit and an amplifier separate type in which the amplifier is separated from the sensor unit and one or more coaxial cables are provided for connecting therebetween. Since the sensor and amplifier units are integrated together, the former type sensor can be readily installed in equipment. However, the size of the sensor unit is disadvantageously increased. On the other hand, since only the sensor unit is installed in the equipment in the latter type, the size of the sensor unit can be reduced. The number of the amplifier separate type sensors have recently been increased in use.
The coaxial cable extending from the sensor unit is connected to the amplifier unit in the amplifier separate type sensor. In connection, a shield wire and a cable core of the coaxial cable are exposed out of outer and inner insulating sheaths respectively. The exposed shield wire and cable core are inserted into two terminal holes formed in an insulating sheaths respectively. The exposed shield wire and cable core are inserted into two terminal holes formed in an insulating enclosure of the amplifier unit, respectively. Thereafter, locking members are firmly inserted into the respective terminal holes so that ends of the shield wire and cable core are held in contact with electrical terminals in the terminal holes respectively.
In the above-described manner of connection, the outer and inner insulating sheaths need to be partially stripped off so that the shield wire and the cable core are exposed out of the respective insulating sheaths. The stripping work is troublesome. Furthermore, since the shield wire and the cable core are flexible, it is difficult to insert them into the respective terminal holes. Additionally, the shield wire and the cable core need to be inserted into the separate terminal holes, which further renders the inserting work troublesome. Furthermore another problem is that since two terminal holes for each coaxial cable need to be formed in the insulating enclosure of the amplifier unit, the size of the amplifier unit is increased.